The ending you’ll see when you finally wrap up Fallout 4’s main questline depends on your choices in the second and third acts. We’ll be explaining these choices and their consequences in detail in the rest of this article, so this is your last chance to avoid some spoilers. Are you ready?
The end game state depends on decisions made during Act Two and Three.
While each ending has its own Act Three mission chain, a major decision point occurs during The Molecular Level at the end of Act Two: If you have the Brotherhood of Steel, Railroad or Minutemen help you build the teleporter, they’ll give you an optional objective of obtaining data about the Institute. Choosing to support a faction in this way unlocks its Act Three questline and ending.
You need to be friendly with each faction in order to have them help you with the teleporter. In the case of the Minutemen and Railroad it’s very easy to join their ranks if you follow the main quest, but you’ll have to seek out the Brotherhood of Steel for yourself or when prompted by a new quest at the end of Act One.
Once you arrive at the Institute during The Molecular Level, you can choose to obtain the data for your faction. If you grab it, you can hand it over to the faction which requested it, continuing with that questline – or leave it alone, and side with the Institute for the fourth ending.
Each of the Act Three questlines involves destroying two factions, and once you’ve knocked off the first one you have one last chance to switch sides, either by betraying the Brotherhood to the Institute or vice versa.
No matter which of the four endings you achieve, you’ll see pretty much the same cinematic at the end; only the Institute’s ending has a different scene. The real difference is the political landscape of the Commonwealth once you’re done: no matter what you do, two factions will be destroyed, locking their quests forever.
Have the Minutemen help you build the teleporter and meet with Father, ending Act Two. Return the Institute data to Sturges. The Minutemen questline will only continue if you help to establish eight key settlements.
Once you’ve met this requirement, the questline will have you attack the Institute and Brotherhood of Steel.
In the wake of this suddenly warlike turn of events, the Minutemen keep the peace in the Commonwealth. Railroad quests will be still be available.
Have the Railroad help you build the teleporter and meet with Father, ending Act Two. Do not aggravate the Institute until prompted to by the Railroad, or this ending will be locked.
To trigger the Railroad questline in Act Three, return the Institute data to them. You’ll need to continue to keep the Institute on friendly terms as the Railroad brings a spy in. You’ll then be sent to help destroy the Brotherhood of Steel and the Institute – and get the chance to adopt a Synth child with Shaun’s memories.
Like the Minutemen, the Railroad ending results in a Commonwealth at liberty, but with more non-hostile synths getting around the place. Minutemen quests will still be available.
This is the only ending the Brotherhood of Steel survives. Have the Brotherhood help you build the teleporter and return the Institute data to them once you have met with Father, ending Act Two.
Although the Brotherhood’s genocidal and totalitarian leanings make this the most morally troubling ending, it’s also totally badass. You have two options for continuing this ending:
Whichever path you take, when the Institute is wiped out, and you find out something pretty amazing about one of your pals.
In the wake of this victory the Brotherhood of Steel work constantly to protect the Commonwealth from threats, which unfortunately include some of its residents. Minutemen quests will still be available.
This ending is available regardless of how you make your way to the Institute. All you need to do is keep on the Institute’s good side, and take one of these two options:
In either case you will have destroyed the Railroad and the Brotherhood of Steel, and eventually end up taking over leadership of the Institute.
The Minutemen are not seen as a threat by the Institute so survive the purge. This ending is somewhat ambiguous as the Institute’s goals are noble enough, but their methods are questionable at best; synths will be enslaved in this ending. Minutemen quests will still be available.
